Introduction
This manual provides comprehensive instructions for the installation, operation, and maintenance of your LUX Pro P521U Programmable 5-2 Day Thermostat. The P521U is designed to offer precise temperature control for your home, featuring programmable settings for weekdays and weekends, and compatibility with various heating and cooling systems. Please read this manual thoroughly before installation and use to ensure optimal performance and safety.
Package Contents
Before beginning installation, verify that all components are present in the package:
- LUX Pro P521U Thermostat Unit
- 2 AA LR6 Batteries
- 2 ST Screws
- 2 Wall Anchors
- Instruction Manuals (this document)
Image: Contents of the LUX Pro P521U package.
Setup and Installation
Proper installation is crucial for the thermostat's functionality. If you are unsure about any steps, it is recommended to consult a qualified HVAC technician.
System Compatibility
Image: System Compatibility Chart.
The P521U thermostat is compatible with a variety of 24V heating and cooling systems. Please review the compatibility chart to ensure your system is supported.
- HEAT (24V) Compatible: Gas/Oil/Electric Furnace (Heating only, Multistage, Single Stage), Heat Pump (with/without Auxiliary Heat), 2-wire Hydronic (Hot Water), 3-wire Hydronic (Hot Water), 750 Millivolt, Gas Fireplaces (24V).
- COOL (24V) Compatible: Cooling only, Single stage cooling.
- NOT Compatible With: Heat Pump Multistage, Cool Multistage, Radiant Ceiling Heat, Electric Baseboards, Portable space heaters, Plug-in air conditioners.
Wiring Instructions
Before wiring, ensure the power to your HVAC system is turned off at the circuit breaker to prevent electrical shock.
- Remove Old Thermostat: Carefully detach your old thermostat from the wall. Note the wire connections to each terminal. It is recommended to label each wire with the corresponding terminal letter before disconnecting.
- Mounting the New Thermostat: Position the new thermostat base plate on the wall. Use the provided screws and wall anchors to secure it.
- Connect Wires: Refer to the appropriate wiring diagram below for your specific HVAC system. Connect the labeled wires to the corresponding terminals on the P521U thermostat. The factory RH-RC jumper wire is typically installed for most systems.
Wiring Diagram #1: 1-Stage or 2-Stage, Heating Only (Including Millivolt)
This diagram illustrates wiring for heating-only systems. Note the RH-RC jumper wire and optional C wire for continuous power.
Wiring Diagram #2: Hot Water Heating Only (With a 3-Wire Zone Valve)
This diagram details wiring for hot water heating systems utilizing a 3-wire zone valve. Pay attention to the A terminal connection for valve control.
Wiring Diagram #3: 1-Stage, Cooling Only
This diagram shows wiring for cooling-only systems. Ensure the G and Y terminals are correctly connected for fan and compressor operation.
Battery Installation
The P521U thermostat is battery-powered (2 AA batteries included).
- Open the battery compartment located on the side or back of the thermostat.
- Insert two new AA alkaline batteries, ensuring correct polarity (+/-).
- Close the battery compartment securely.
Note: Rechargeable batteries are not recommended as they may cause inaccurate battery level readings or premature power loss.
Operating Instructions
The P521U thermostat features a clear digital display and intuitive controls for managing your home's temperature.
Thermostat Controls Overview
Image: P521U Control Panel Diagram.
- LCD Display Screen: Shows current temperature, time, day, and system status. Features a backlight for visibility.
- Fan Mode Switch (FAN): Controls fan operation (AUTO/ON).
- System Mode Switch (TEMPERATURE): Selects system mode (HEAT/OFF/COOL).
- UP/DOWN Buttons: Adjust temperature settings and navigate programming menus.
- HOLD Button: Maintains the current temperature indefinitely, overriding the program schedule.
- Set Slide Switch (SET): Used for setting Day/Time, Temperature Program, and Air Filter reminders.
- EMER Button: Accesses certain setup functions (functionality may vary based on system type).
- NEXT Button: Advances through programming steps and menu options.
Setting Current Day and Time
- Slide the SET switch to DAY/TIME.
- Use the UP/DOWN buttons to adjust the time.
- Press NEXT to advance to the day setting.
- Use the UP/DOWN buttons to select the current day.
- Slide the SET switch back to RUN to save and exit.
Programming the Schedule (5-2 Day)
The P521U allows for separate programming for weekdays (5 days) and weekends (2 days), with 2 or 4 periods per day.
- Slide the SET switch to TEMP PROG.
- The display will show the first programming period (e.g., "MORN" for weekdays).
- Use the UP/DOWN buttons to set the desired temperature for this period.
- Press NEXT to set the start time for this period using the UP/DOWN buttons.
- Repeat steps 3 and 4 for all desired periods (MORN, DAY, EVE, NIGHT) for weekdays.
- After programming all weekday periods, the thermostat will automatically advance to the weekend programming. Repeat the process for Saturday and Sunday.
- Once all programming is complete, slide the SET switch back to RUN.
Tip: The thermostat may include a "COPY" feature to duplicate a day's program to another day, simplifying the programming process. Consult the full online manual for details on this feature.
Manual Temperature Hold
To temporarily override the program schedule and maintain a specific temperature:
- Adjust the temperature using the UP/DOWN buttons to your desired setting.
- Press the HOLD button. The display will show "HOLD" to indicate the program is suspended.
- To cancel the hold, press the HOLD button again or slide the SET switch to RUN. The thermostat will resume its programmed schedule.
Maintenance
Battery Replacement
The thermostat will display a low battery indicator when the AA batteries need replacement. Replace batteries promptly to ensure continuous operation.
- Open the battery compartment.
- Remove the old batteries.
- Insert two new AA alkaline batteries, observing correct polarity.
- Close the battery compartment.
Important: The thermostat features battery-free memory storage, so your programmed settings will be retained during battery replacement.
Air Filter Monitor
The P521U includes a programmable air filter life timer. When the filter needs changing, an indicator will appear on the display. Refer to the full online manual for instructions on setting and resetting this reminder. Regular filter changes improve system efficiency and air quality.
Troubleshooting
If you encounter issues with your P521U thermostat, review the common problems and solutions below. For more detailed troubleshooting, refer to the complete online manual available on the LUX website.
| Problem | Possible Cause | Solution |
|---|---|---|
| Display is blank or dim. | Dead or low batteries. Incorrect battery installation. | Replace with fresh AA alkaline batteries, ensuring correct polarity. |
| Thermostat not controlling HVAC system. | Power to HVAC system is off. Incorrect wiring. System mode switch set to OFF. | Check circuit breaker for HVAC system. Verify wiring connections against diagrams. Ensure system mode is set to HEAT or COOL. |
| Temperature readings seem inaccurate. | Thermostat located near heat sources/drafts. Calibration issue. | Ensure thermostat is not exposed to direct sunlight, drafts, or heat-emitting appliances. Refer to the online manual for temperature calibration instructions. |
| Programming is difficult or not intuitive. | Unfamiliarity with programming steps. | Carefully follow the programming steps in this manual or the detailed online manual. Utilize the "COPY" feature if available. |
| HVAC system cycles too frequently (short cycling). | Temperature differential (swing) is set too low. | Adjust the temperature differential/cycle-rate setting. A wider differential reduces cycling frequency. Refer to the online manual for this advanced setting. |
Specifications
| Brand | LUX |
| Model Name | P521U-010 |
| Controller Type | Push Button |
| Special Feature | Low Voltage |
| Color | White |
| Specific Uses For Product | Air Conditioner, Furnace, Heat Pump |
| Temperature Control Type | Programmable |
| Connectivity Technology | IR |
| Included Components | Pro P521U-010 Programmable 5-2 Day Thermostat; 2 Heat, 1 Cool |
| Power Source | Battery Powered (2 AA batteries included) |
| Item Weight | 1.76 ounces |
| Voltage | 24 Volts |
| Material | Plastic |
| Display Type | Digital |
| Control Method | Remote (via buttons) |
| Mounting Type | Wall Mount |
| Product Dimensions | 5.38 x 3.38 x 1.13 inches |
| UPC | 021079125210 |
Warranty and Support
For warranty information, technical support, or to access the complete digital instruction manual, please visit the official LUX website or contact LUX customer service.
You can find more information and support resources at the LUX Brand Store on Amazon.
